The present invention relates to a plastic spectacle lens for sight curing.
Before being machined for fitting to spectacle frames, plastic spectacle lenses are generally circular, and particular directions such as a principal meridian are not determined yet. According to specific operations, specification of directivity of each of lenses, such as the direction of the principal meridian, becomes necessary. In practice, the direction, such as direction of the principal meridian, of each lens must be specified in the following events: for example, determination of the power and the astigmatism axis of the lens; half coloring to color a half of the lens; and fitting of the lens to a spectacle frame in a correct direction.
In progressive power multi-focus lens, it is preferable to previously indicate information of the classification thereof on the lens surface. There may be a case where lenses of a specific characteristic are taken out from many lenses having different characteristics.
In spite of such needs, blanks of conventional plastic spectacle lenses have no indicia to indicate directional instructions, a class and a power. To determine the direction of a lens, an instrument, such as a lens meter, must be used. Alternatively, each lens is accompanied with an instruction slip indicating a directivity, a classification and a power thereof, and production of the lens must be done referring to the instruction slip. This deteriorates productivity of spectacles. Moreover in case of losing an instruction slip, it is hard to quickly know the information of the lens.